Acetals from acrylonitrile, carbon monoxide, hydrogen, and alcohols



Patented May 9, 1950 ACETALS FROM ACRYLONITRILE, CARBON MONOXIDE,HYDROGEN, AND ALCOHOLS Paul Latrell Barrick, Wilmington, and Albert AlanPavlic, Claymont, Del., assignors to E. I. du Pont de Nemours & Company,Wilmington, Del., a corporation of Delaware No Drawing. ApplicationAugust 10, 1948, Serial No. 43,537

6 Claims. 1

This invention relates to the synthesis of cyanoproplonaldehyde acetals.

No satisfactory method has yet been devised for the synthesis ofacetals, i. e., diethers of 1,1- glycols, containing nitrile groups inthe molecule. The common procedure hitherto employed for the preparationof acetals consists in reacting aldehydes with alcohols underessentially anhydrous conditions in the presence of acidic catalystssuch as hydrogen chloride. Nitriles under these same conditions,however, also react with alcohols to form iminoethers and, therefore,the application of this orthodox method for cyanoacetal manuiacture fromthe corresponding aldehydo-nitrile intermediates is impractical.

This invention has as an object the provision of a process for thepreparation of cyanopropionaldehyde acetals. Other objects will appearhereinafter.

These objects are accomplished by the following invention wherein amixture of carbon monoxide and hydrogen is reacted in the presence of ahydrogenation catalyst with a mixture comprising acrylonltrile and asaturated alcohol, preferably in the chemical proportion whereby atleasttwo alcoholic hydroxyls are present for each ethylenic bond 'of theacrylonitrile. The products have the formula (R'O)2CH2CH2CN wherein theR groups are both alkyl or together form an alkylene radical. Theinvention is carried out by heating the reactants at reactiontemperatures and pressures within the range of 80-300 C. and aboveatmospheres with a hydrogenation catalyst, preferably one selected fromthe metals of VlIIth group of the periodic table. Cobalt and rutheniumcatalysts are particularly eflective. I A more specific and preferredpractice oi the invention comprises reacting a mixture of carbonmonoxide and hydrogen in the presence 01' a cobalt hydrogenationcatalyst with a mixture comprising acrylonitrile and an alkanol of oneto four carbon atoms. The preferred temperature lies'between 100 and 200C. With acrylonitrile pressures of 75-150 atmospheres do not give thedesired result and pressure of 600 atmospheres or higher, e. g., 1200atmospheres are employed.

The more detailed practice of the invention is illustrated by thefollowing examples wherein parts are given by weight unless otherwisespecilied.

Example I Into a silver-lined high pressure reaction vealel oi 400 cc.capacity was charged 75 parts of 'acrylonitrile, one part 01'tertiary-butylcatechol.

ten parts of a reduced cobalt-thoria catalyst parts cobalt-18 partsthoria, 200 parts kieselguhr) and parts of methanol. The vessel was thenclosed and pressured to 230 atmospheres with hydrogen, then to 400atmospheres with carbon monoxide and heated with shaking at C. for onehour, during which period the pressure was maintained between 600 and900 atmospheres with carbon monoxide.

At the end of this time the vessel was cooled and excess gas was bledoff. The contents were discharged into a stripping still heated byxylene vapor as a heat exchange material and distilled. After removal ofthe methanol at atmospheric pressure, the product was distilled at thetemperature of boiling xylene under pressures down to 1 mm. This latterfraction on redistillation in a precision still yielded 59 parts ofcyanopropionaldehyde dimethyl acetal as a colorless oil boiling at 90-9lC./14 mm.

Analysis: Calculated for CsHnNOzZ C, 55.80%; H, 8.58%; N, 10.85%. Found:C, 55.64%;55.51%; H, 8.69%, 8.66%; N, 10.72%, 10.90%.

Example II Example ill In order to illustrate the flexibility of thecarbon monoxide-hydrogen ratios, the apparatus described in Example Iwas charged with ,60 parts of acrylonitrile, 120 parts of methanol, twoparts of hydroquinone, and ten parts of cobalt-thoria catalyst. Thevessel was then closed, pressured to 230 atmospheres with carbonmonoxide then to 400 atmospheres with hydrogen andheated one hour at C,with agitation during which period the vessel was repressured withhydrogen to maintain the pressure between 800, to 1,000 atmospheres.Following a work-up as described above there was obtained 25 parts ofcyanopropionaldehyde dimethyl acetal distilling at 89-90 C./l2 mm.

Example IV Ethylene glycol (110 parts) was substituted for the methanol(120 parts) in the process 01 Example I and with '15 parts ofacrylonitrile, two parts 3 of hydroquinone, and ten parts ofcobalt-thoria catalyst was'likewise reacted under the same carbonmonoxide-hydrogen pressures. The reaction was carried out at 175 C. forone hour. Twelve parts of cyanoprcpionaldehyde ethylene acetaldistilling at ll-75 C./6 mm.; nn 1.4248, was obtained by distillation ofthe reaction mixture. Although the process of the invention has beenillustrated with methanol and ethylene glycol, it is, in general,applicable to saturated primary and secondary monohydric and dihydricalcohols, i. e., to alcohols having from one to two hydroxyls, thehydroxyls being on carbons attached to at least one hydrogen. Primarymonohydric alcohols are preferred, particularly the alkanols of from oneto four carbon atoms, 1. e., methanol to the 'butanols. Moreparticularly, methanol,

ethanol, ethylene glycol, and the propylene glycols are preferredbecause of their availability andsatisfactory reactivity. Theunsaturated alcohols, such as allyl, methallyl and crotyl alcohols, havebeen found unsuitable as alcohol components for the production ofacetals by the proces of this invention. These alcohols, because oftheir rearrangement to aldehydes under the conditions of the process andbecause of the condensation of these aldehydes to high boiling and.

sometimes intractable products, are unsuitable.

- In the process of this invention, the saturated hydroxylic reactant,for example, an alkanol or alkanediol, is preferably present in achemical proportion of at least two active hydroxyls per mol ofacryig-nitrile. Likewise, carbon monoxide .should be employed in anamount such that it is at least molarly equivalent initially to theacrylo-.

nitrile being carbonylated, and although not absolutely essential, it ispreferable, because in general of improved yields, to use molal excessesof carbon monoxide. For example, the molal ratio, of, acrylonitrile tocarbon monoxide can vary from 1:1 to 1:20 or more, the preferred ratiobeing The molal ratio of carbon monoxide to hydrogen can range fromabout 122 from 1:2 to 1:10.

to 2:1. In general, however, it is preferable to keep .the molal ratioof the two gases at about 1:1. Mixtures of the saturated alcohols canalso housed.

As already indicated the minimum pressure required to effect reaction isat least 600 atmospheres. The pressure required also depends on suchfactors as the nature of the alcoholic reactant, temperature, catalyst,etc. With acrylonitriie and methanol pressures of 75 to 150 atmospheresdo not give the desired result and pressures in the range of 600 to 1200atmospheres or higher are employed.

Hydrogenation catalysts, and particularly those 1 comprising metals ofthe VIIIth group of the perlodic table of elements, are suitable for thepr0- duction of acetals by the process of this invention.

More particularly, hydrogenation catalysts of cobalt and ruthenium arepreferred. The eiiectiveness of these catalystsfor the purpose of this 1invention may be enhanced by the addition of 4 certain activators, e.g., the dlilicultly reducible metal oxides such as those of thorium,magnesium, chromium, and aluminum, such oxides being employed in anamount of from 5 to 150 per cent of the weight of the activehydrogenating metal. These hydrogenation catalysts are generallyemployed in excess of 0.1% (based on the weight of the acrylonitrile),and preferably between 1 and 15% since these amounts usually give thebest results.

The products of this invention are useful as intermediates for thepreparation of pharmaceuticals and dyestuffs, and as pest controlagents.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed for obvious modifications will occur to those skilled in theart.

What is claimed is: I

1. A process which, comprises heating, at reaction temperature withinthe range 100-200 C. and at a pressure of at least 600 atmospheres,acrylonitrile with, per mol of nitrile, at least two mols of an alkanolof one to four carbons, at least one mol of carbon monoxide and at leastone mol of hydrogen in the presence of a cobalt hydrogenation catalyst,said alcohol being initialhydrogenation catalyst, the methanol. beingini tially present in the amount of at least two mols per mol ofnitrile.

3. A process which comprises heatinggatreaction temperature and pressurewitIiinth'e nge of so-aoo c. and 600-1200 atmospheres, and in thepresence of a hydrogenating catalyst, acrylonitrile with, "per mole ofacryloni't'rile, at least one mol of carbon monoxide, at least one molof. hy-

drogen and, initially present in the amount of at least two equivalentsof hydroxyl per mol of acrylonitrile, a saturated aliphatic alcoholhaving hydrogen on carbinol carbon.

4. Process of claim 3 wherein the 'flcohol is an alkanediol.

5. Process of claim 3 wherein the alcohol is ethylene glycol.

6. Process of claim 3 wherein the catalyst'is"a ruthenium hydrogenationcatalyst.

. PAUL LATRELL BARRI'CK...

ALBERT ALAN PAVLIC.

REFERENCES CITED UNITED STATES PATENTS Name Date Graham et al. Mar. 9.1948 Number

1. A PROCESS WHICH COMPRISES HEATING, AT REACTION TEMPERATURE WITHIN THERANGE 100-200*C. AND AT A PRESSURE OF AT LEAST 600 ATMOSPHERES,ACRYLONITRILE WITH, PER MOL OF NITRILE, AT LEAST TWO MOLS OF AN ALKANOLOF ONE TO FOUR CARBONS, AT LEAST ONE MOL OF CARBON MONOXIDE AND AT LEASTONE MOL OF HYDROGEN IN THE PRESENCE OF A COBALT HYDROGENATION CATALYST,SAID ALCOHOL BEING INITIALLY PRESENT IN THE AMOUNT OF AT LEAST TWO MOLSPER MOL OF NITRILE.